Slake, assuage (6)
I believe the answer is:
quench
This clue is a double definition.
'slake' is the first definition.
(I know that slake can be written as quench)
'assuage' is the second definition.
(I know that assuage can be written as quench)
(Other definitions for quench that I've seen before include "Extinguish (a fire)" , "End a thirst" , "Damp down" , "Slake - assuage" , "Douse" .)